Seafloor spreading occurs at Feature A and subduction occurs at Feature B
Explanation:
The mid-ocean ridge is the place where the ocean floor spreads. This feature can be found where two plates are moving away from one another. The gap that they live between them enables the magma from the mantle to easily rise up. As the magma comes to the ocean floor, it cools off and creates new crust. As the magma continues to come out, it builds up, creating an underwater mountain chain, known as a mid-ocean ridge.
The ocean trench on the other side, is the place where one plate moves below another plate, thus subducting. As the plate is subducting, it reaches the mantle layer, so its crust is melted by the high temperatures, resulting in the destruction of that crust.
